The present invention relates to a process for surface fluorinating polymers to form substantially fluorinated surfaces and to the fluorinated polymers so-produced.
Prior to the present invention, attempts have been made to fluorinate polymers utilizing fluorine gas. Unfortunately, when utilizing fluorine under relatively mild conditions of temperature, pressure and fluorine concentration, wherein polymer degradation is not substantial, the reaction time to effect fluorination is relatively large as shown by Clark et al, Journal of Polymer Science: Polymer Chemistry Edition, Volume 13, pages 857-890 (1975). The products of prior fluorination procedures utilizing fluorine gas include a number of species containing only partial fluorine substitution for hydrogen. This is also undesirable since the presence of hydrogen tends to increase the free energy of the polymer surface, thereby not forming low energy surfaces of the type that characterize perfluorinated polymers. An improved surface fluorination process has been proposed in U.S. Pat. No. 4,264,750 to fluorinate hydro-carbon or amide polymers by exposing the polymer to a source of fluorine in a cold plasma. The present invention offers an alternative process using ultraviolet radiation to substantially assist the fluorination in the surface region of the polymer.